1. Field of the Invention
This invention relates to a multiple dosing device for liquids and more particularly to such a device for castable reaction resin compounds used in the manufacture of cast and encapsulated mechanical and electrical components such as housings, molds, transformers, capacitors, light emitting diodes, voltages multiplier cascades, and cup type rectifiers.
2. Description of the Prior Art
Multiple dosing devices in which a liquid is apportioned simultaneously into several equal parts are known. When large numbers of componets are made, economy dictates the need for multiple casting.
Some dosing devices employ the suction pump principle whereby the liquid is drawn into the device by suction created by pulling back pistons housed in cylinders immersed in a liquid filled dish ("Physik fuer Rechnische Berufe"-- Physics for Technical Vocations, 13th ed., No. 48c). After being filled, the cylinders are moved to a position above the cavities to be filled and the liquid is ejected by means of the piston. Since the cylinders lie in an open dish and are thus exposed to the atmosphere, the liquids can react chemically with gases or moisture in the air. Such reactions degrade the quality of the liquids which, in the case of hexahydrophthalic acid, absorb moisture from the air, or in the case of amines, absorb carbon dioxide. On the other hand, low boiling point liquids evaporate and in this way volatile and possibly injurious components of the liquids may be released into the air. If the cycle frequency is great, complete filling no longer occurs and the multiple dosing becomes nonuniform.
Other known dosing devices accomplish the dosing from a given tank by simultaneous operation of several parallel connected valves (Physik fuer Technische Berufe, No. 51a, b). With this method the material simply flows out. Since the flow conditions vary and are nonreproduceable, the dosing becomes nonuniform.
Dosing can also be accomplished by means of a hose pump with several flexible dosing tubes. However, hoses have different elastic performance and particularly have only moderate restoring force, and as a result, the dosing outputs differ in volume especially in the case of highly viscous liquids. Since hoses fatigue and in time break, the liquids may escape and contaminate the production facility. Furthermore not all materials can be pumped.
Other known multiple dosing devices use mechanically driven synchronous multiple piston pumps having spherical, conical, disk or slide valves. Plunger pumps or diaphragm pumps with spherical, conical, disk or slide valves are also known ("Chemische Verfahrenstechnik"--Chemical Process Technology--by A. G. Kassatkin, 1953, Vol. I, pp. 104-05, 121-22). Such assemblies, however, require a great deal of technical support and in particular the range of the required nozzle spacing is limited.